Method and apparatus for determining a relative position of a processing head with respect to a substrate with a structure

ABSTRACT

A method and apparatus wherein a substrate is provided with a preformatted structure, with structural elements arranged in a matrix, wherein the matrix extends in an X-direction and Y-direction, wherein a processing head is provided, wherein a camera is provided which is connected with the processing head and which comprises at least one series of sensors arranged along a main line, wherein the camera scans the substrate and thereby provides at least one one-dimensional camera signal, wherein, for real-time determining at least the X-position and the Y-position of the structure with respect to the camera, the said main line includes an angle with the X-direction and with the Y-direction, wherein the angle is chosen such that the camera signal contains spatially separated X-position information and Y-position information and that the X-position information and the Y-position information can be separated from the sensor signal with the aid of signal processing.

The invention relates to a method and an apparatus for determining therelative position of a processing head with respect to a substrate witha preformatted structure, with structural elements arranged in a matrix,wherein the matrix extends in an X-direction and Y-direction. Thestructure may be a relief structure but may also be a printing whichprovides a color difference structure on the substrate.

Although the invention is not limited thereto, in order to give a betteridea, this should particularly be understood to involve substratedimensions of at least 10 mm*10 mm, while the structural elements, suchas for instance pixel wells of a substrate intended for manufacturing anOLED, have dimensions of the order of 20-500 micrometers, and while thedistance between the structural elements is in the range of 2-40micrometers. With regard to the accuracy with which the relativeposition of the substrate with respect to the processing head is to beprovided, this should be understood to involve an accuracy which is ofthe order of 1 micrometer. For this, it likewise holds that theinvention is not limited to such accuracies.

Observing the position of a structure on a substrate is, for instance,carried out with the manufacture of displays, for instance OLEDs. Forthis, see for instance EP-A-1 351 325. With the manufacture of a displayor another type of device, determining the position of, for instance, arelief structure is important for inter alia controlling a readingand/or writing laser or for controlling an inkjet printer head. A greataccuracy is desired to have new structures fit to the existingstructures as well as possible, so that the quality of the display orthe other type of device is as high as possible. The problem withfinding a position of a structure already present is that the accuracyof positioning sometimes leaves much to be desired. When the position ofa structure already present on the substrate has not been determinedaccurately, a next layer on the substrate cannot be applied accurately.This results in a reduced quality of the display or other type of deviceand therefore in extra rejects in the production, which is unfavorableto the production costs.

The present invention contemplates a method with the aid of which theposition of a structure on a substrate can be observed in a simplemanner, while this is done very accurately, while the method forobservation can be carried out quickly and inexpensively.

To this end, the invention provides a method wherein a substrate isprovided with a preformatted structure, with structural elementsarranged in a matrix, wherein the matrix extends in an X-direction andY-direction, wherein a processing head is provided, wherein a camera isprovided which is connected with the processing head and which comprisesat least one series of sensors arranged along a main line, wherein thecamera scans the substrate and thereby provides at least oneone-dimensional camera signal, wherein, for real-time determining atleast the X-position and the Y-position of the structure with respect tothe camera, the above-mentioned main line includes an angle with theX-direction and with the Y-direction, while the angle is chosen suchthat the camera signal contains spatially separated X-positioninformation and Y-position information and that the X-positioninformation and the Y-position information can be separated from thesensor signal with the aid of signal processing.

The invention further provides an apparatus for observing a structure ona substrate and for carrying out an operation on a substrate, whichsubstrate is provided with a preformatted structure, with structuralelements arranged in a matrix, wherein the matrix extends in anX-direction and Y-direction, wherein the apparatus is provided with asubstrate support and with a processing head, wherein a displacementmechanism is provided for relative displacement of the processing headwith respect to the substrate, wherein, with the processing head, atleast one camera is connected which comprises at least one series ofsensors arranged along a main line, wherein the camera is operativelydisplaced with respect to the substrate and thereby scans the substratefor providing at least one one-dimensional camera signal, wherein, forreal-time determining at least the X-position and the Y-position of thestructure with respect to the camera, the above-mentioned main lineincludes an angle with the X-direction and with the Y-direction, whereinthe angle is chosen such that the camera signal contains spatiallyseparated X-position information and Y-position information, wherein theapparatus is provided with a control which is provided with asignal-processing module which is arranged for separating the X-positioninformation and the Y-position information from the sensor signal withthe aid of signal processing.

With this method and apparatus, as a result of the fact that the mainline of the camera includes an angle with the X-direction and with theY-direction, a large number of structural element boundaries are locatedbelow the main line of the camera. These are structural elementboundaries extending in X-direction as well as in Y-direction. Thepositions of the intersections of the structural element boundaries andthe line camera are spatially separated over the length of the main lineof the camera. In the further signal processing, all these spatiallyseparated position information can be used for determining the relativeX-position and the relative Y-position of the structure with respect tothe camera. As a result, a very good signal-to-noise ratio (SNR) isobtained with the measurements and, in addition, a great accuracy isobtained with the position determination of the relative X-position andthe relative Y-position.

According to a further elaboration of the method and the apparatus, theangle of the main line with respect to the X-direction and theY-direction is chosen or set such that the camera operatively provides mspatially separated X-signals and n spatially separated Y-signals.Preferably, therein, m and n are mutually different prime numbers.Preferably, the signal-processing module of the apparatus is arrangedfor accurately deriving the relative X-position and Y-position of the atleast one camera with respect to the substrate with the aid of signalprocessing comprising a fast Fourier transformation (FFT). Instead of afast Fourier transformation, the signal processing may also comprise adiscrete sine/cosine transformation. Here, the frequencies correspondingwith the m spatially separated X-signals and the n spatially separatedY-signals will then be subjected to such a sine/cosine transformation inorder to derive the relative X-position and Y-position with respect tothe camera therefrom. In particular when m and n are mutually differentprime numbers, there will be little cross talk in the signal between theX-position information-providing pulses and the Y-positioninformation-providing pulses and therefore deriving the X-positioninformation and the Y-position information can be done relatively simplyand accurately.

According to a further elaboration, a method and an apparatus areprovided wherein the relative X-position of the substrate structure withrespect to the camera is derivable from the m^(th) result of the FFTprocessing of the camera signal and wherein the relative Y-position ofthe substrate structure with respect to the camera is derivable from then^(th) result of the FFT processing. Here, m is the number of spatiallyseparated structural element boundaries extending in Y-direction whichare simultaneously observed by the camera and n is the number ofspatially separated structural element boundaries extending inX-direction which are simultaneously observed by the camera.

Preferably, during a scanning pass, in which the relative X-position andY-position are determined, further, an operation on the substrate iscarried out with the processing head. This operation may, for instance,comprise an inkjet printer operation, a lighting, an ablation operation,and/or placing components on the substrate.

According to a further elaboration of the invention, the X-positioninformation, which is derived from the camera signal, is used forcorrecting the relative X-position of the processing head with respectto the substrate.

According to a still further elaboration of the invention, theY-position information, which is derived from the camera signal, is usedfor timing the operation, such as for instance timing the release ofliquid by an inkjet printer head, the timing of the lighting by alighting processing head, the timing of an ablation operation and/or thetiming of the release of components.

According to a further elaboration of the invention, the processing headis rotatable about a centerline extending at right angles to thesubstrate. It can thus be realized that the pitch in X-direction of, forinstance, the nozzles of a processing head designed as an inkjet printerhead is geared to the pitch of the substrate structure in X-direction.

According to a still further elaboration of the invention, the at leastone camera is preferably rotatable with respect to the processing headabout a centerline extending at right angles to the substrate. Thus, theangle of the above-mentioned main line of the camera can be set suchthat the camera signal contains spatially separated X-positioninformation and Y-position information.

Preferably, the camera is a line camera. Such line cameras comprise aseries of sensors arranged in line, for instance 1024 sensors togetherforming a line sensor. By using an objective for the line sensor, adesired part of the structure, for instance a linear part having alength of 1 mm, can be imaged on the line sensor.

The invention will now be explained in more detail on the basis of anexemplary embodiment, with reference to the drawing, in which:

FIG. 1 shows an arrangement of an exemplary embodiment of an apparatusaccording to the invention; and

FIG. 2 shows a top plan view of a substrate with the differentsuccessive camera positions shown therein.

The exemplary embodiment shown in FIG. 1 shows a substrate 1 which issupported by a substrate support which can displace the substrate 1 inX-direction and Y-direction. In the present exemplary embodiment, thesubstrate 1 is intended for manufacturing a display therefrom. On thesubstrate, an orthogonal matrix structure is present which is, in thepresent exemplary embodiment, a relief structure comprising pixel wells.The pixel wells have dimensions which are in the range of 20-500micrometers. The distance between the edges of the pixel wells is in therange of 2-40 micrometers. The substrate 1 has a length and a width ofat least 10 mm*10 mm but may also be much larger, for instance 1000mm*2000 mm.

The accuracy with which the X-position information and the Y-positioninformation are to be provided is of the order of approximately 1micrometer.

FIG. 1 also shows a processing head 2 which is provided with fourcameras 3, which are, in the present exemplary embodiment, designed asline cameras. The line cameras each comprise one series of sensorsarranged along a main line. Each line camera observes, for instance, alength of approximately 1 mm and contains, for instance, 1024 sensorsarranged next to one another along the main line. Such a line cameraprovides a one-dimensional signal which is subjected to signalprocessing. It is noted that two-dimensional CCD cameras may also beused, while, however, each time a one-dimensional signal of the CCDcamera—i.e. a signal coming from a series of sensors arranged along onemain line—will be subjected to signal processing.

In an alternative embodiment, the substrate may also be arrangedstatically and the processing head 2 may be arranged movably inX-direction and Y-direction. In another alternative elaboration, thesubstrate 1 may, for instance, be arranged movably in Y-direction andthe processing head 2 may, for instance, be arranged displacably inX-direction and vice versa.

The processing head 2 is pivotal about a centerline extending at rightangles to the substrate 1. The cameras 3 are pivotal with respect to theprocessing head 2 about centerlines extending at right angles to thesubstrate.

Further, a motion controller 4 is provided which controls thedisplacement of the substrate support. The Figure further shows aprocessing head driver 5—in the present exemplary embodiment, theprocessing head is an inkjet printer head and the processing head driver5 is an inkjet printer head driver 5. Reference numeral 6 designates asignal-processing module.

The signal-processing module 6 has the one-dimensional camera signals 7coming from the cameras 3 as input information and also has geometricalknowledge 8 of the structure applied to the substrate 1. On the basis offast Fourier transformation or discrete sine/cosine transformation ofthe one-dimensional camera signal of each camera 3, the relativedisplacement 9 of the X-position of the substrate 1 with respect to theexpected position is determined. This deviation 9 in X-direction mayalso be referred to by the term actual tracking deviation. The actualtracking deviation 9 thus determined is used as an input signal for themotion controller 4. On the basis of fast Fourier transformation of theone-dimensional signal of each camera 3, the signal-processing module 6also determines the relative displacement of the Y-position of thesubstrate with respect to the expected position. On the basis of thisY-position information, a print trigger signal 10 is transmitted to themotion controller 4 by the signal-processing module 6. In the presentexemplary embodiment, per pixel on the substrate 1, one print trigger 10is transmitted to the motion controller 4. From the motion controller 4,a second print trigger signal 11 related to the clock is transmitted tothe inkjet printer head driver 5 which controls the different nozzles ofthe inkjet printer head 2.

In the present exemplary embodiment, the substrate length extends inY-direction and the substrate width extends in X-direction. In ascanning pass, by a relative displacement of the processing head 2 withthe cameras 3 with respect to the substrate 1, the substrate is scannedin Y-direction over the whole substrate length. Then, a relativedisplacement of the substrate 1 with respect to the processing head 2 inX-direction is realized, after which a next scanning pass in Y-directionfollows. The step of a scanning pass in Y-direction and a displacementin X-direction is repeated until the substrate 1 has been scanned overthe whole substrate width.

The relative displacement in Y-direction may be either a stepwisedisplacement or a continuous displacement at a speed in the range of0-40 m/s.

The sampling frequency of the camera signal may be in the range of 1 kHzto 2 MHz.

When there are structural elements having dimensions of the order ofmagnitude of about 150 micrometers and a scanning speed of approximately0.4 m/s, a sampling frequency of 10 kHz is sufficient to preventaliasing of signal pulses.

The main line of the at least one camera includes an angle with theX-direction and includes an angle with the Y-direction. Theabove-mentioned angles deviate from 0 and from 90 degrees and have beenchosen such that the camera signal contains spatially separatedX-position information and Y-position information and that theX-position information and the Y-position information can be separatedfrom the sensor signal with the aid of signal processing.

FIG. 2 shows, in top plan view, the successive positions A, B, . . . Zof a line camera 3 with respect to a substrate 1 provided with a matrixstructure M. In that exemplary embodiment, the substrate 1 is providedwith a pixel structure in which the pixels have dimensions of 50*150micrometers. The line camera 3 having a length of approximately 1 mmincludes an angle with the X-direction of approximately 49 degrees. Thisresults in the line camera intersecting five pixel boundaries inY-direction and intersecting thirteen pixel boundaries in X-direction.During scanning, each line camera provides m spatially separatedX-signals and n spatially separated Y-signals, with m=13 and n=5. Due tothe fact that, in the present exemplary embodiment, m and n are bothprime numbers which are, in addition, mutually different, no or hardlyany coinciding pulses for pixel boundaries in X-direction and pixelboundaries in Y-direction will occur, so that no or hardly any crosstalk occurs in the signal. Therefore, per line camera position A, B, . .. Z, FIG. 2 shows no or hardly any positions on the line camera 3 whichcoincide with an intersection of pixel boundaries in X-direction andY-direction. Both in X-direction and in Y-direction, the signals of thestructural element boundaries are spatially separated well. It will beclear that the angle is different when the dimensions of the structuralelements are different. When the pixels, for instance, have dimensionsof 300*300 micrometers, a suitable angle which the main line of the linecamera can include with the X-direction is 33.7 degrees. With thatangle, with a line camera having a length of approximately 1 mm, threespatially separated pixel boundary intersections can be observed inX-direction and two spatially separated pixel boundary intersections canbe observed in Y-direction. With unsuitably chosen angles, the spatialseparation can decrease considerably (for instance with 0 and with 90degrees) or a considerable cross talk can occur in the observation ofthe pixel boundaries in X-direction and the pixel boundaries inY-direction. With square pixels, an angle of 45 degrees is, forinstance, particularly unfavorable because of the large extent of crosstalk in the signal.

During the signal processing in the signal-processing module 6, therelative X-position of the substrate structure with respect to thecamera is derived from the m^(th) result of the FFT processing of thecamera signal and the relative Y-position of the substrate structurewith respect to the camera is derived from the n^(th) result of the FFTprocessing, with m being the number of pixel boundaries extending inY-direction observed per line camera and with n being the number ofpixel boundaries extending in X-direction observed per line camera.

The amplitude of the m^(th) result and the n^(th) result is anindication of the reliability of the signal and the phase information ofthe m^(th) result and the n^(th) result is proportional to the relativeX-position and the relative Y-position, respectively.

Due to the fact that, with this method, of all structural elementboundaries located below the main line of the camera, the informationprovided thereby is used, a very good signal-to-noise ratio (SNR) isobtained with the measurements and, in addition, a great accuracy isobtained in the position determination of the relative X-position andthe relative Y-position.

The invention is not limited to the exemplary embodiment described and,within the framework of the invention, as defined by the claims, variousvariants are possible. Thus, the method and the apparatus may also beused for determining the position of a structure applied to a substrate,the substrate being intended for a different end product. Here, optionsto be considered are electronics, memories, biomedical analysis arrays,TFT structures for LCD and placing components on a PC board. Thestructural elements on the substrate do not need to be pixel wells butmay also be formed by other elements detectable with light, such as forinstance electronic components in a chip, color filter elements and thelike. Also, the path of scanning over the substrate may be varied inmany manners. Instead of scanning in Y-direction and stepwisedisplacement in X-direction, scanning may also take place in an obliquedirection, i.e. in a direction which includes an acute angle with theX-direction or the Y-direction. As already indicated, scanning may takeplace at a continuous speed and scanning may take place stepwise.Instead of a relief structure with pixel wells or similar structuralelements, a structure in the form of a printing may also have beenapplied to the substrate. The cameras then observe contrast differencesinstead of, for instance, height differences which are determined by theboundaries of the relief structural elements. As already indicatedhereinabove, instead of an inkjet printer head, the processing head mayalso comprise a lighting head, an ablation head or a processing head forplacing components. The lighting may, for instance, take place withvisible light, UV radiation, infrared radiation, X-ray or the like. Whenthe structural elements have dimensions larger than 300 micrometers, forobtaining a good accuracy and a reliable signal, the length of the mainline along which the series of sensors of the camera are arranged needsto be increased.

In the exemplary embodiment described, the structural elements arearranged in an orthogonal matrix. However, the relative position of astructure of which the structural elements are arranged in anon-orthogonal matrix can also be determined with the method andapparatus according to the invention. Here, options to be considered arematrix structures with a round, trapezium or honeycomb structure.

1. A method comprising: providing a substrate with a preformattedstructure, with structural elements arranged in a matrix, wherein thematrix extends in an X-direction and a Y-direction, the structuralelements having boundaries, providing a processing head, providing acamera that is connected with the processing head and that comprises atleast one series of sensors arranged along a main line, using the camerato scan the substrate, thereby providing at least one one-dimensionalcamera signal, wherein, for real-time determination of at least theX-position and the Y-position of the structure with respect to thecamera, said main line includes an angle with the X-direction and withthe Y-direction, wherein the angle is chosen such that the camera signalcomprises X-position information and Y-position information regardingthe structural element boundaries, and determining the X-position andthe Y-position of the preformatted structure relative to the camerathrough signal processing of the camera signal.
 2. A method according toclaim 1, wherein the angle is chosen such that the camera providesX-position signal information on m spatially separated structuralelement of the matrix boundaries that extend in the Y-direction, andY-position information on n spatially separated structural elementboundaries of the matrix that extend in the Y direction.
 3. A methodaccording to claim 2, wherein m and n are mutually different primenumbers.
 4. A method according to claim 1, wherein the signal processingcomprises a fast Fourier transformation.
 5. A method according to claim1, wherein the signal processing comprises a fast discrete sine/cosinetransformation.
 6. A method according to claim 3, wherein the signalcomprises a fast Fourier transformation of the camera signal, whereinthe X-position of the preformatted structure relative to the camera isdetermined from the m^(th) result of the fast Fourier transformation ofthe camera signal, and wherein the relative Y-position of thepreformatted structure relative to the camera is determined from then^(th) result of the fast Fourier transformation of the camera signal.7. A method according to claim 1, wherein a substrate length extends inthe Y-direction and a substrate width extends in the X-direction,further comprising: using the camera to scan the substrate with pluralscanning passes, wherein, in a scanning pass, by a relative displacementof the camera with respect to the substrate, the substrate is firstscanned in the Y-direction over the whole substrate length, and then bya relative displacement of the substrate with respect to the camera inthe X-direction, after which displacement a next scanning pass in theY-direction follows.
 8. A method according to claim 7, furthercomprising: repeating scanning passes in the Y-direction anddisplacements in the X-direction until the substrate has been scannedover the whole substrate width.
 9. A method according to claim 7,further comprising: carrying out, during a scanning pass, a furtheroperation on the substrate with the processing head.
 10. A methodaccording to claim 9, wherein the operation is an inkjet printeroperation.
 11. A method according to claim 9, wherein the operationcomprises a lighting.
 12. A method according to claim 9, wherein theoperation comprises an ablation operation.
 13. A method according toclaim 9, wherein the operation comprises placing components.
 14. Amethod according to claim 7, wherein the speed of the relativedisplacement in Y-direction is either a stepwise displacement or acontinuous displacement at a speed in the range of 0-40 m/s.
 15. Amethod according to claim 1, wherein the sampling frequency of thecamera signal is in the range of 1 kHz to 2 kHz.
 16. A method accordingto claim 1, further comprising: using the X-position of the preformattedstructure determined from the camera signal for correcting a relativeX-position of the processing head with respect to the substrate.
 17. Amethod according to claim 9, further comprising: using the Y-position ofthe preformatted structure from the camera signal for timing theoperation, such as for instance timing the release of liquid by aninkjet printer head, timing the lighting by a lighting processing head,an ablation operation and/or the release of components.
 18. A methodaccording to claim 1, wherein the substrate has dimensions of at least10 mm*10 mm, wherein the structural elements have dimensions of theorder of 20-50 micrometers, and wherein the distance between thestructural elements is in the range of 2-40 micrometers.
 19. A methodaccording to claim 1, wherein the accuracy with which the X-position andthe Y-position of the preformatted structure relative to the camera areof the order of 1 micrometer.
 20. An apparatus for carrying out anoperation on a substrate, which substrate is provided with apreformatted structure, with structural elements having boundaries andarranged in a matrix, wherein the matrix extends in an X-direction andY-direction, wherein the apparatus is provided with: a substratesupport; a processing head; a displacement mechanism for relativedisplacement of the processing head with respect to the substrate; atleast one camera is connected to the processing head, said cameracomprising at least one series of sensors arranged along a main line,the camera being operatively displaceable with respect to the substrateand configured to thereby scan the substrate for providing at least oneone-dimensional camera signal, wherein, for real-time determination ofat least an X-position and a Y-position of the preformatted structurewith respect to the camera, said main line includes an angle with theX-direction and with the Y-direction, wherein the angle is chosen suchthat the camera signal comprises X-position information and Y-positioninformation regarding spatial separation of the boundaries of thestructural elements in the matrix, and a control including asignal-processing module that is arranged for determining the X-positionand the Y-position of the preformatted structure relative to the camerathrough signal processing of the camera signal.
 21. An apparatusaccording to claim 20, wherein the angle of the main line with respectto the X-direction and the Y-direction is set such that the camerasignal provides X-position information on m spatially separatedstructural element boundaries of the matrix that extend in they-direction and Y-position information on n spatially separatedstructural element boundaries of the matrix that extend in theX-direction.
 22. An apparatus according to claim 21, wherein m and n aremutually different prime numbers.
 23. An apparatus according to claim20, wherein the signal-processing module of the apparatus is arrangedfor carrying out a fast Fourier transformation.
 24. An apparatusaccording to claim 20, wherein the signal-processing module of theapparatus is arranged for carrying out a fast discrete sine/cosinetransformation.
 25. An apparatus according to claim 22, wherein thesignal processing module of the apparatus is arranged for carrying out afast Fourier transformation, wherein the signal-processing module isarranged for determining the X-position of the preformatted structurerelative to the camera from the m^(th) result of the fast Fouriertransformation of the one-dimensional camera signal, and for determiningthe Y-position of the preformatted structure relative to the camera fromthe n^(th) result of the fast Fourier transformation processing of theone-dimensional camera signal.
 26. An apparatus according to claim 20,wherein the processing head is rotatable about a centerline extending atright angles to the substrate.
 27. An apparatus according to claim 20,wherein the at least one camera is rotatable with respect to theprocessing head about a centerline extending at right angles to thesubstrate.
 28. An apparatus according to claim 20, wherein the controlis arranged for using the X-position of the preformatted structuredetermined from the camera signal for correcting the relative X-positionof the processing head with respect to the substrate.
 29. An apparatusaccording to claim 20, wherein the control is arranged for using theY-position of the preformatted structure determined from the camerasignal for timing the operation, such as for instance timing the releaseof liquid by an inkjet printer head, the timing of the lighting by alighting processing head, the timing of an ablation operation and/or thetiming of the release of components.